Protective caps or covers have been used in various applications to control the movement of liquids. For example, a cap may be used on a vessel containing a liquid to minimize the evaporation of the liquid and to prevent accidental spillage that may occur when the vessel is moved. As another example, components such as electric components or connectors that are immersed in or expand to liquids must be protected with a cover so as to avoid deleterious effects that could be caused by exposure of the component to the liquid.
One area in particular where electric connectors may be immersed in a liquid, and therefore in need of protection, is in a nuclear reactor.
Nuclear reactors typically include various forms of instrumentation. For example, in-core instruments can be positioned near the fuel bundle or core to measure various parameters associated with the core""s performance. These instruments can include, for example, core exit thermocouples and rhodium detectors. The core exit thermocouples measure the temperature of fluid as it exits the core, and the rhodium detectors measure neutron density, which is related to the power level in the core.
Maintenance activities in the reactors sometimes involve moving the core or removing the reactor vessel internals. During such activities the chamber or vessel in which the in-core instrument""s electrical connectors are located is flooded with water to minimize the potential for radiation doses to workers performing the maintenance activity. Moreover, the connectors oftentimes have to be de-mated or disconnected as part of the maintenance activities, leaving one end of the connector open and exposed to the surrounding environment.
Prior to the time the vessel is flooded, the exposed ends of the de-mated connectors must be covered or sealed in order to isolate and protect them from the water. These ends are typically protected with a metal cap.
Traditionally, these metal caps have included an o-ring to provide a seal between the connector and the cap in order to protect the exposed end of the connector from the water in which it is immersed. Experience has indicated that the metal caps may leak, particularly if they are not properly installed, or because the o-ring has become loose or disengaged. Moreover, maintenance activities oftentimes involve working with long handled tools which are dipped into the water to perform certain tasks. These tools occasionally impact the metal caps, which can dislodge them from the connector if they are not properly installed. Consequently, the fact that the metal caps are not properly installed oftentimes lead to undesirable results. A cap that leaks or is dislodged will allow water to flood the exposed end of the connector, which may then need to be reworked to replaced to recover its critical electrical capabilities.
The metal caps usually include a lanyard attached to the connector or a nearby surface to capture the cap in the event it is dislodged from the connector. However, the lanyards are oftentimes cut or otherwise removed because they can interfere with, and extend the time needed, for maintenance activities. Time can be of the essence in the nuclear reactor environment, because of both the possibility of radiation exposure to workers, and the loss of revenues while the power plant is off-line. Consequently, an incentive exists to cut any lanyard that is interfering with maintenance activities.
However, if the lanyard is cut and the cap becomes dislodged from the connector, there is nothing to prevent it from sinking into the surrounding body of water. Recovering the cap can be difficult, not only because it sinks into the water, but also because it is typically made with a color that blends into the color of the installation environment. An unrecovered metal cap is undesirable because it poses a potential for foreign object damage, including damage to the fuel assembly and reactor coolant pumps. This in turn can lead to decreased reactor performance and safety risks which are preferably avoided.
From the foregoing, it is seen that a need exists for an improved means of protecting de-mated instrumentation electrical connectors from a surrounding body of water during maintenance activities in nuclear reactors.
Apparatus is provided that can be installed onto an exposed end of an instrumentation electrical connector, to protect the exposed end of the connector from a surrounding body of liquid. The apparatus can include a shell having a closed first end formed from a liquid resistant shell material, a second end, and a skirt portion extending therebetween. The second end can have an opening therein for insertion onto the exposed end of the connector. A compression operable seal can be positioned in a seal groove adjacent an inside surface of the skirt portion and adjacent the first end. The seal groove can include a trough adjacent the inside surface. A connection means on the internal surface can be adapted to matingly engage an external surface on the connector, and to move the shell material towards the exposed end of the connector when the apparatus is moved to an installed condition. When the apparatus is in the installed condition, the shell material can compress the seal against the exposed end to form a substantially leak proof barrier between the exposed end of the connector and the body of liquid.
Either the shell, seal, or both can have a specific gravity less than the specific gravity of the liquid, but in either case the shell and seal have a combined specific gravity that is less than the specific gravity of the liquid to give the apparatus flotation capability. At least a portion of an outside surface on the shell can be of a color that contrasts with the color of the installation environment.
According to further aspects of the invention, the seal can include a wave washer, and the shell can include a visual installation position indicator and an outside surface with a gripping means.
According to another aspect of the invention, a method is provided for protecting an exposed end of an instrumentation connector in a nuclear reactor from a surrounding body of liquid. The method includes extending an internal surface on a shell over an external surface on the connector, removably connecting the internal surface to the external surface, providing at least a portion of the shell with a liquid resistant shell material, positioning the shell material over the exposed end of the connector, positioning a compression operable seal between the shell material and the exposed end of the connector, and moving the shell to an installed condition wherein the seal is compressed between the shell material and the connector to form a substantially leak-proof seal.